All-optical dispersive Fourier analysis for ultrafast user localization at 50 MHz in beam-steered optical wireless communication

Beam-steered optical wireless communication (OWC) enables high-capacity indoor links where real-time user localization is crucial. We propose and experimentally demonstrate an all-optical method for ultrafast localization operating at 50 MHz in wavelength-controlled beam-steered OWC. The scheme exploits the mapping between user position and the wavelength of retro-reflected signals. Instantaneous wavelength identification is achieved through all-optical frequency coding and dispersive Fourier transform (DFT), allowing user positions to be derived from the time interval between two optical pulses without high-speed detection or digital processing. A theoretical model confirms a linear relation between instantaneous frequency and pulse interval, validated by numerical and experimental results. By shifting Fourier analysis entirely into the optical domain, the method offers a simple, low-cost, and energy-efficient solution for real-time and ultrafast user-specific localization in beam-steered OWC systems.